Over the past decade, several companies started commercializing compact medical devices that interface directly with smartphones and tablets or other portable computers. Of particular interest are ultrasound probes. They plug-in directly into the computing device and use its processing capabilities to display high quality diagnostic ultrasound images in real-time, rivaling traditional machinery only found at large clinical institutions. By virtue of their versatility and portability, these technologies carry profound benefits for critical care. However, one major obstacle remains. Mastering how to use an ultrasound transducer to diagnose a patient requires extensive training and hands-on experience. This invention introduces a new hardware accessory that allows using the same system for both clinical applications and self-directed training through simulation.